The present invention relates to medical devices. Specifically, the invention relates to a device for removing blood clots or thrombus from body vessels, such as small arteries associated with the brain.
Mechanical thrombectomy is a procedure that has been in widespread use for many years. Typical thrombectomy devices are balloons that are inflated in a vessel, then withdrawn to pull clots into a sheath which can be withdrawn from the patient to remove the clots. Other devices are simple open ended catheters into which a clot is aspirated and removed from the patient. Another thrombectomy device employs a basket device that is opened within the clot so that the clot becomes captured in the basket, which can be retrieved along with the clot. Still other devices use a small corkscrew shaped device that is collapsed inside a catheter, passed through the clot, pushed out of a delivery sheath allowing the device to expand, then retracted, capturing the clot for removal. Some corkscrew devices are simply “screwed” into the clot, then retracted into a catheter for removal.
All of these devices may, however, have certain disadvantages. For example, the balloon catheter devices are first advanced through the clot before they can be inflated and retracted. The process of penetrating the clot with the balloon catheter device tends to push the clot deeper into the arterial circulation where it becomes even more difficult to remove. This issue also occurs with basket and corkscrew devices that are collapsed into an outer delivery sheath and passed through the clot before they can be deployed and retracted. The action of pushing a device through the center of the clot pushes the clot deeper into the artery and sometimes fragments the clot, making it even more dangerous as an embolus. The corkscrew devices that are screwed into the clot usually have a smooth rounded tip to prevent the corkscrew from penetrating the vessel wall or otherwise damaging the vessel wall as it is screwed into the clot. With these devices, however, the smooth, rounded central tip does not screw into the clot, but instead is pushed into the clot and then the remainder of the corkscrew is screwed into the clot. This results in a pushing force on the center of the clot and a pulling force on the periphery of the clot. These counter forces tend to macerate or fragment the clot and result in only a small part of the clot being captured. The small corkscrew devices with sharp tips can screw directly into the clot; however, they can penetrate the vessel wall just as easily as they can penetrate and capture the clot. As a result, the use of such devices is very risky and thus seldom performed. If a bead or ball is applied to the tip of the device that is large enough to protect the vessel wall, it will be so large that it will tend to push the clot distally, deeper into the artery rather than penetrate the clot such that the clot can be captured and removed.
Another issue associated with conventional thrombectomy devices is that they are typically too large and too stiff for use in the small tortuous vessels in the brain. Some of the conventional devices also use a central mandrel wire or some other structure for support, which displace clots, making it difficult to capture all the clot material.